Eye Sight

Calm Moment: Yoga for Your Eyes
Courtesy of Organic Connections From new recipes to e-mails to funny cat videos, our devices inform and entertain us. In fact, the average American spends nearly ten hours a day taking it all in. But during all  …
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Surge in Pollen May Lead to Dry Eyes
High pollen levels in the spring are linked to dry eye syndrome, a recent study suggests. Dry eye is a common condition caused by either decreased tear production or increased tear evaporation. Symptoms include burning,  …
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Nutrients Linked to Eye Health
Studies have determined certain nutrients have positive effects on eye health. The research focus is on Vitamins C and E, found in high levels in the eye lens; lutein and zeaxanthin, which are concentrated in the  …
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More Computer Time May Be Causing Nearsightedness in U.S. Kids
Posted December 30, 2015 By Julianne Cuba HealthDay Reporter THURSDAY, Dec. 24, 2015 (HealthDay News) — Children who spend lots of time indoors and on computers and other electronic devices may be raising  …
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Related Terms

  • Age-related macular degeneration, allergic conjunctivitis, aqueous humor, arcus senilis, astigmatism, bacterial conjunctivitis, blepharitis, calcific band keratopathy, chlamydial conjunctivitis, choroid, ciliary body, ciliary muscles, conjunctiva, conjunctivitis, cornea, corneal abrasion, dry eye, ectropion, eye inflammation, giant papillary conjunctivitis, gonococcal conjunctivitis, hyperopia, iris, keratitis, keratoconjunctivitis sicca, lacrimal glands, laser-assisted in situ keratomileusis, LASIK, Leber’s disease, lupus, myopia, nasolacrimal duct, neonatal conjunctivitis, non-infectious conjunctivitis, ophthalmia neonatorum, ophthalmia neonatorum prevention, ophthalmologists, ophthalmoscopy, optometrists, photoreactive keratectomy, photoreceptors, photorefractive keratectomy, pinkeye, presbyopia, PRK, punctum, retinal examination, retinitis pigmentosa, rheumatoid arthritis, sclera, scotomas, Sjögren syndrome, slit-lamp examination, thimerosal, uveitis, viral conjunctivitis, vision problems, visual field loss, vitrectomy, xerophthalmia.


  • Any condition affecting the eye is classified as an eye disorder. Eye disorders can affect any part of the eye, including the eyelids, eyelashes, iris, pupil, lens, and the sclera (the “white” of the eye). Nerves, muscles, and blood vessels that surround the eye can also be affected by eye disorders.
  • Eye disorders may include any of the following: vision problems, including astigmatism (vision difficulties due to a football-shaped cornea), diabetic retinopathy, myopia (nearsightedness), or hyperopia (farsightedness); conjunctivitis (inflammation of the conjunctiva); uveitis (inflammation of the uvea); keratitis (inflammation of the cornea); xerophthalmia (dry eye); glaucoma (an increase in intraocular pressure); age-related macular degeneration; and cataract (an opacity that develops in the crystalline lens of the eye). Some of these conditions, such as astigmatism myopia, glaucoma, macular degeneration, cataracts, and retinitis pigmentosa, have been linked to genetic abnormalities. Treatment and prognosis varies, depending on the specific condition.
  • Please see individual Natural Standard condition monographs on glaucoma, cataracts, retinopathy, and macular degeneration for more information on these eye disorders.

Signs and symptoms

  • Vision problems: Symptoms of vision problems include vision loss, altered eye movements, eye pain, visual field loss, bulging eyes, double vision, and headaches. Eye symptoms may involve changes in vision, changes in the appearance of the eye, or an abnormal sensation in the eye. Eye symptoms typically develop as a result of a problem in the eye but occasionally indicate a problem elsewhere in the body.
  • Conjunctivitis: The most common signs and symptoms of conjunctivitis include redness in one or both eyes and itchiness in one or both eyes. Other common symptoms include blurred vision and sensitivity to light, a gritty feeling in one or both eyes, a discharge in one or both eyes that forms a crust during the night; and tearing.
  • Uveitis: Symptoms include light sensitivity, blurring of vision, pain, and redness of the eye. Uveitis may come on suddenly with redness and pain, or it may be slow in onset with little pain or redness, but with gradual blurring of vision.
  • Xerophthalmia (dry eye): Symptoms of dry eye range form mild irritation and foreign body sensation to severe discomfort with sensitivity to light.
  • Keratitis: Keratitis usually makes the eyes very painful and watery, bloodshot, and sensitive to light. The condition is often accompanied by blurred or hazy vision. If the herpes simplex virus is the cause, the individual will notice a small white spot on the cornea.
  • Corneal abrasion: A corneal abrasion should be suspected if the individual has sustained an injury to the eye. Some of the symptoms experienced may include: a sensation of a foreign body in the eye (this feeling sometimes develops a few hours later rather than immediately after the apparent injury); tearing of the eyes; blurred vision or distortion of vision; eye pain when exposed to a bright light; and spasm of the muscles surrounding the eye causing the individual to squint.
  • Retinitis pigmentosa: Each individual with retinitis pigmentosa may experience symptoms differently, depending upon the severity and progression of the condition. Some individuals with retinitis pigmentosa experience a slow, very progressive loss of vision, while others lose their visual ability much more quickly and severely. Other common symptoms may include: difficulty seeing in poor light (such as at dusk or in a dimly lit area) or in the dark; a diminished visual field, either central vision (a condition called macular dystrophy) or peripheral vision (sometimes referred to as tunnel vision); difficulty reading print (with a loss of central vision); difficulty deciphering detailed images (with a loss of central vision); difficulty with stumbling or tripping over objects not seen; clumsiness (with a loss of peripheral vision); and glare. The symptoms of retinitis pigmentosa may resemble other eye diseases, such as glaucoma.


  • A person who experiences eye symptoms should be checked by a doctor. However, some eye diseases cause few or no symptoms in their early stages, so the eyes should be checked regularly (every 1-2 years or more frequently if there is an eye condition). Healthcare professionals that deal with eye disorders include: opticians – they dispense glasses and do not diagnose eye problems and optometrists – they perform eye exams and may diagnose eye problems. Optometrists may prescribe glasses and contact lenses. In some states, they prescribe eye drops to treat diseases. Ophthalmologists are medical doctors who diagnose and treat diseases that affect the eyes. Ophthalmologists may also provide routine vision care services, such as prescribing glasses and contact lenses.
  • An individual with eye or vision problems describes the location and duration of the symptoms, and then the doctor examines the eye, the area around it, and possibly other parts of the body, depending on the suspected cause. An eye examination usually includes refraction, a visual field testing, ophthalmoscopy, a slit lamp examination, and tonometry. A doctor may take a sample of eye secretions from the conjunctiva for laboratory analysis to determine which form of infection the individual has and how best to treat it. A doctor will ask about any eye pain or discomfort.
  • Visual acuity test: Acuity refers to the sharpness of vision or how clearly the individual sees an object. In this test, the eye doctor checks to see how well the individual reads letters from across the room. The eyes are tested one at a time, while the other eye is covered. Using a chart (called a Snellen eye chart) with progressively smaller letters from top to bottom, an eye doctor determines if the individual has 20/20 vision or less acute vision.
  • Slit-lamp examination: A slit-lamp allows the eye doctor to see the structures at the front of the eye under magnification. The microscope is called a slit lamp because it uses an intense line of light (or a slit) to illuminate the cornea, iris, lens, and the space between the iris and cornea. The slit allows the doctor to view these structures in small sections, which makes it easier to detect any small abnormalities.
  • Retinal examination: In a retinal examination, an eye doctor puts dilating drops in the eyes to open the pupils wide and provide a bigger window to the back of the eyes. Using a slit lamp or a special device called an ophthalmoscope, the doctor can examine the lens for signs of a cataract, glaucoma, or damage to the retina. Dilating drops usually keep the pupils open for a few hours before their effect gradually wears off. Until then, the individual will probably have difficulty focusing on close objects, while distance vision is generally less affected. With the pupils open this wide, individuals may want sunglasses for their trip home, especially if it is a bright day. Also, it may be safer to let someone else do the driving.
  • Genetic testing: Genetic testing is available for some genetic eye disorders. For example, genetic testing is available for several genetic mutations associated with retinitis pigmentosa, including: RLBP1, RP1, RHO, RDS, PRPF8, PRPF3, CRB1, ABCA4, and RPE65.


  • Vision problems:
  • Eyeglasses or contact lenses are the treatment for vision disturbances, such as astigmatism, hyperopia, and myopia.
  • Lenses with bifocal or progressive addition lenses (PALs) are the most common correction for presbyopia. Bifocal means two points of focus: one section corrects for distant vision and the other section corrects for near vision. There are multifocal contact lenses available also for individuals with presbyopia.
  • Progressive addition lenses are similar to bifocal lenses, but they offer a more gradual visual transition between the two prescriptions, with no visible lines between them.
  • Reading glasses are another choice. Unlike bifocals and PALs, which most people wear all day, reading glasses are typically worn just during close work. If the individual wears contact lenses, an eye doctor can prescribe reading glasses that can be worn while the contacts are in. Reading glasses may be purchased over-the-counter (OTC) at a retail store or higher-quality versions are also available by prescription from an eye doctor.
  • Because the human lens continues to change as an individual grows older, the presbyopic prescription will increase over time as well.
  • Surgery: Surgical options to treat vision problems are available. LASIK, which stands for laser-assisted in situ keratomileusis, is one of the most popular modern treatments for a number of refractive errors, including myopia, hyperopia, and astigmatism. LASIK has a number of benefits; aside from the short amount of time required for the procedure itself, the LASIK procedure allows for rapid healing with minimal discomfort. Laser vision correction takes only about 15 minutes to complete. Most individuals see well enough to drive within 24 hours of their LASIK treatment.
  • Although LASIK is an option for most individuals with vision problems, there are certain groups of people who are not good candidates for the surgery, including: those under the age of 21 as most individual’s eyes are still developing when they are younger, and it is important that the prescription has stabilized before performing LASIK surgery to correct the vision; those with autoimmune conditions such as lupus, Sjogren’s syndrome, and rheumatoid arthritis; those with scarred corneas or a history of herpes infection in the eye; and women who are pregnant or breastfeeding. Often, prescriptions will fluctuate dramatically during and after pregnancy. Women should wait until after they are done nursing before undergoing LASIK.
  • First, the individual’s prescription is entered into a computer that controls the laser. After the eye is prepared and numbed with anesthetic drops, the surgeon creates a flap in the cornea using an extraordinarily precise instrument called a microkeratome. The individual may feel some pressure during this portion of the procedure. The laser is then positioned over the eye, where it will emit small, controlled bursts of energy. Depending on the desired outcome of the surgery, small amounts of corneal tissue will be removed in order to change the focus of the eye. For the duration of the laser’s operation, the surgeon will closely monitor the eye through a surgical microscope to make sure the desired prescription has been achieved. Next, the flap is returned to its original position. The flap will self-adhere and does not typically require sutures. The major advantages of corneal flap creation are that healing is faster and that discomfort is greatly reduced.
  • It is recommended by healthcare professionals to go directly home and sleep (or at least keep the eyes closed) for about four hours. The eyelids will help the corneal flap to continue the bonding process. After this time period, it is essential that the individual keep their eyes lubricated with the drops provided the surgeon and follow all of the postoperative instructions.
  • Photoreactive keratectomy (PRK): Photoreactive keratectomy (PRK) is similar to LASIK in that a laser is used to reshape the cornea to change the way that it focuses. However, in PRK, no flap is created in the cornea. Instead, a thin layer of epithelial, or surface, cells is removed to expose the corneal tissue underneath. PRK is effective for patients with myopia and astigmatism. PRK is an alternative for those who are not suitable candidates for LASIK, including those whose corneas are too thin to accommodate a flap.
  • Because there is no corneal flap to protect the treated area, patients who undergo PRK can expect to experience more discomfort and a slightly longer recovery period than those who undergo LASIK. Surgeons will likely place a bandage contact lens on the affected eye to protect it during the first few days after surgery. Once the healing period is over, however, PRK patients should enjoy the same amount of success and satisfaction as with other procedures.
  • Conjunctivitis:
  • A doctor may prescribe antibiotic eyedrops, such as Neosporin®, if the infection is bacterial. The infection should clear within several days of starting treatment. Antibiotic eye ointment, in place of eyedrops, is sometimes prescribed for treating bacterial conjunctivitis in children. An ointment is often easier to administer to an infant or young child than are eyedrops. It is important to use the medication as prescribed to prevent recurrence of the infection.
  • Viral conjunctivitis cannot be treated with antibiotic eyedrops or ointment. Like a common cold, individuals can use an over-the-counter (OTC) remedy, such as naphazoline (Vasoclear®, Naphcon®) to relieve some symptoms. Individuals may notice a worsening of symptoms in the first three to five days. Signs and symptoms should gradually clear on their own. It may take up to two to three weeks from the time of infection for the virus to go away.
  • If the irritation is allergic conjunctivitis, a doctor may prescribe one of many different types of eyedrops. These may include antihistamines, decongestants, mast cell stabilizers, steroids, and anti-inflammatory drops.
  • Xerophthalmia (Dry eye):
  • In treating dry eye, the first thing to do is to remove or reduce the cause. Reducing contact lens wear time and taking breaks from intense visual work are just two such examples. The use of over-the-counter (OTC) artificial teardrops is the primary treatment for dry eye. If the individual has chronic dry eye, it is important to use the drops even when the eyes feel fine, to keep them lubricated. If the eyes dry out while sleeping, there are thicker lubricants, such as ointments, which can be used at night.
  • Temporary punctal occlusion: A temporary punctal occlusion is a procedure that closes the ducts that drain tears out of the eye. A plug that will dissolve quickly is inserted into the tear drain of the lower eyelid. This is a temporary procedure, done to determine whether permanent plugs can provide an adequate supply of tears.
  • Permanent punctal occlusion: Permanent punctal occlusion is used if temporary plugging of the tear drains works well. Permanent punctal occlusion involves the use of silicone plugs placed in the tear ducts. The plugs will hold tears around the eyes as long as they are in place. They can be removed. Rarely, the plugs may come out spontaneously or migrate down the tear drain. Many individuals find that the plugs improve comfort and reduce the need for artificial tears.
  • Restasis: Restasis® is a prescription eye drop used for the treatment of chronic dry eye. It helps the eyes increase their own tear production.
  • Other medications: Other medications, including ophthalmic anti-inflammatory eye drops and eye ointments (steroids and non-steroids), may also be beneficial in some cases.
  • Surgery: If needed, the ducts that drain tears into the nose can be permanently closed to allow more tears to remain around the eye. This is done with a local anesthetic on an outpatient basis. There are no limitations in activity after having this surgery.
  • Uveitis:
  • Treatment of uveitis depends in large part on what’s causing the condition. Often, a doctor prescribes anti-inflammatory medications, such as ophthalmic corticosteroids or non-steroidal antiinflammatory drugs. A doctor also could give the corticosteroids by pill or by injection into the eye. If uveitis is caused by an infection, antibiotics, antiviral medications, or some other medicine may be given with or without corticosteroids to bring the infection under control. If uveitis is caused by an underlying condition, treatment will focus on treating that specific condition.
  • The part of the eye affected by uveitis, either the front (anterior) or back (posterior) of the uvea, may determine the duration of the condition. With proper treatment, anterior uveitis can clear up in a matter of days to weeks. Posterior uveitis, on the other hand, may last several months or years and could permanently alter vision.
  • If the uveitis responds poorly to corticosteroids or becomes severe enough to threaten vision, the individual may need to try a different kind of medication, such as an immunosuppressive or cytotoxic agent.
  • Vitrectomy, surgery to remove the jelly-like material in the eye (vitreous), may sometimes be necessary for diagnosis and treatment of uveitis.
  • Keratitis:
  • Minor corneal infections such as keratitis are commonly treated with anti-bacterial or anti-fungal eye drops. If the problem is more severe, a person may receive more intensive prescription antibiotic treatment to eliminate the infection and may need to take steroid eye drops to reduce inflammation. With residual corneal scarring or thinning, corneal transplantation may be necessary to restore vision. Early treatment may help reduce the risk of complications. Frequent visits to an eye care professional may be necessary for several months to eliminate the problem.
  • Retinitis pigmentosa:
  • Effective treatments for retinitis pigmentosa are currently unknown. Retinal microchip implants have been investigated for treating blindness associated with retinitis pigmentosa. In early research, Artificial Silicon Retina (ASR) microchips in patients with retinitis pigmentosa have shown promising improvements in visual function. The ASR microchips measure 2mm in diameter and one-thousandth of an inch thick and contain approximately 5,000 microscopic solar cells that convert light into electrical impulses. These cells are intended to replace photoreceptors in the retina, which are damaged in patients with retinitis pigmentosa. Study results are variable and additional research is needed to better understand the role of retinal microchip implants in patients with retinitis pigmentosa.

Integrative therapies

  • Strong scientific evidence:
  • Vitamin A: Vitamin A is a fat-soluble vitamin that is derived from two sources: preformed retinoids and provitamin carotenoids. Retinoids, such as retinal and retinoic acid, are found in animal sources such as livers, kidneys, eggs, and dairy produce. Carotenoids like beta-carotene (which has the highest vitamin A activity) are found in plants such as dark or yellow vegetables and carrots. Vitamin A deficiency can lead to various eye disorders including Bitot’s spot, the buildup of keratin debris in the conjunctiva. Oral vitamin A is the treatment of choice for xerophthalmia (dry eye) due to prolonged vitamin A deficiency and should be given immediately once the disorder is established.
  • Vitamin A toxicity, or hypervitaminosis A, is rare in the general population. Vitamin A toxicity can occur with excessive amounts of vitamin A taken over short or long periods of time. Consequently, toxicity can be acute or chronic. An infant with acute toxicity can develop a bulging fontalle (the soft spot on the head) and symptoms similar to a brain tumor. Adults experience less specific symptoms such as headache, dizziness, fatigue, malaise, blurry vision, bone pain and swelling, nausea, and/or vomiting. Severe toxicity can lead to eye damage, high levels of calcium, and liver damage. Persons with liver disease and high alcohol intake may be at risk for hepatotoxicity from vitamin A supplementation. Smokers who consume alcohol and beta-carotene may be at an increased risk for lung cancer or cardiovascular disease.
  • Good scientific evidence:
  • Iodine: Povidone-iodine solutions appear to have broad-spectrum activity against bacteria and have been used in the management of childhood bacterial conjunctivitis. Povidone-iodine solutions may also be used for ophthalmia neonatorum, a type of bacterial conjunctivitis with eye discharge that occurs during the first month of life, and may be as effective as other anti-bacterial solutions such as neomycin-polymyxin B-gramicidin. Medical supervision is recommended and povidone-iodine solutions are not an effective treatment for viral conjunctivitis. Prior to ophthalmologic procedures, povidone-iodine solutions are used for sterilization for ocular surgery infection prevention.
  • Reactions can be severe and deaths have occurred with exposure to iodine. Avoid iodine-based products if allergic or hypersensitive to iodine. Do no use for more than 14 days. Avoid Lugol solution and saturated solution of potassium iodide (SSKI, PIMA) with hyperkalemia (high amounts of potassium in the blood), pulmonary edema (fluid in the lungs), bronchitis, or tuberculosis. Use cautiously when applying to the skin because it may irritate/burn tissues. Use sodium iodide cautiously with kidney failure. Avoid sodium iodide with gastrointestinal obstruction. Iodine is safe in recommended doses for pregnant or breastfeeding women. Avoid povidone-iodine for perianal preparation during delivery or postpartum antisepsis.
  • Vitamin A: Retinitis pigmentosa is a genetic disorder that affects night vision. Early symptoms include night blindness and progressive loss of vision over time. Based on recent findings, vitamin A in the palmitate form has been recommended in patients with retinitis pigmentosa.
  • Vitamin A toxicity, or hypervitaminosis A, is rare in the general population. Vitamin A toxicity can occur with excessive amounts of vitamin A taken over short or long periods of time. Consequently, toxicity can be acute or chronic. An infant with acute toxicity can develop a bulging fontalle (the soft spot on the head) and symptoms similar to a brain tumor. Adults experience less specific symptoms such as headache, dizziness, fatigue, malaise, blurry vision, bone pain and swelling, nausea, and/or vomiting. Severe toxicity can lead to eye damage, high levels of calcium, and liver damage. Persons with liver disease and high alcohol intake may be at risk for hepatotoxicity from vitamin A supplementation. Smokers who consume alcohol and beta-carotene may be at an increased risk for lung cancer or cardiovascular disease.
  • Unclear or conflicting scientific evidence:
  • Acupuncture: Acupuncture is a technique of inserting and manipulating needles into “acupuncture points” on the body with the aim of restoring health and well-being, e.g. treating pain and diseases.The practice of acupuncture originated in China 5,000 years ago. Today, it is widely used throughout the world and is one of the main pillars of Chinese medicine. Although a few clinical studies support the use of acupuncture for keratoconjunctivitis sicca (dry eyes), there is insufficient evidence for a clear understanding of the benefits of acupuncture for this disorder.
  • Needles must be sterile in order to avoid disease transmission. Avoid with valvular heart disease, medical conditions of unknown origins, or infections. Acupuncture should not be applied to the chest in patients with lung diseases or on any area that may rely on muscle tone to provide stability. Avoid use in patients with needle phobias. Use cautiously with bleeding disorders, neurological disorders, seizure disorders, or diabetes. Use cautiously in elderly or medically compromised patients. Use cautiously in patients who will drive or operate heavy machinery after acupuncture. Use cautiously if taking anticoagulants.
  • Chelation therapy: EDTA chelation became well known during the 1950s when it was proposed as a method to cleanse the blood and blood vessel walls of toxins and minerals. The technique involves infusing a chemical called ethylene diamine tetraacetic acid (EDTA) into the blood. The therapy is sometimes given by mouth and occasionally other chemicals may be used. EDTA is commonly used in ophthalmology as a calcium-binding agent in calcific band keratopathy. However, there is a lack of available evidence for this use. More studies are needed.
  • Chelation may be dangerous in people with heart, kidney, or liver disease or with conditions affecting blood cells or the immune system. Use during pregnancy, breastfeeding, or in children may also be dangerous due to potential toxic effects. Serious side effects have been associated with chelation therapy, such as dangerously low calcium blood levels, damage to bone marrow, which decreases the ability to make new blood cells, kidney damage (with elevated creatinine levels), very low blood pressure, fast heart rate, increased risk of bleeding or blood clots (including interference with the effects of the blood thinning drug warfarin [Coumadin®]), bacterial blood infections, seizures, allergic or immune system reactions, heart rhythm abnormalities, and unstable blood sugars. Other side effects may include fever, nausea, vomiting, gastrointestinal upset, excessive thirst, sweating (diaphoresis), headache, decreased thyroid function, fatigue, low white blood cell count (leukopenia), or low blood platelet count (thrombocytopenia). Severe reactions have occurred in which people have stopped breathing. Although deaths have been reported in people receiving chelation, it is not clear that chelation therapy was the direct cause.
  • Chiropractic: Chiropractic is a healthcare discipline that focuses on the relationship between musculoskeletal structure (primarily the spine) and body function (as coordinated by the nervous system), and how this relationship affects the preservation and restoration of health. The broad term “spinal manipulative therapy” incorporates all types of manual techniques, including chiropractic. There are several published articles with positive findings from case series and case reports suggesting that chiropractic manipulation may be of benefit for vision problems from diverse origins. However, randomized controlled trials are currently lacking. There is also not enough reliable scientific evidence to conclude the effects of chiropractic techniques for the recovery or prevention of visual field loss.
  • Avoid with vertebrobasilar vascular insufficiency, aneurysms, arteritis, or unstable spondylolisthesis. Avoid use on post-surgical areas of para-spinal tissue. Use cautiously with acute arthritis, brittle bone disease, conditions that cause decreased bone mineralization, bleeding disorders, migraines, or if at risk of tumors or metastasis of the spine. Use extra caution during cervical adjustments. Avoid if pregnant or breastfeeding due to a lack of scientific data.
  • Chondroitin: Chondroitin was first extracted and purified in the 1960s. It is currently manufactured from natural sources (shark/beef cartilage or bovine trachea) or by synthetic means. Chondroitin is sometimes used as a component of eye solutions used for keratoconjunctivitis, corneal preservation, and intraocular pressure. These solutions should only be used under the supervision of an ophthalmologist. Additional study is needed to better determine the effectiveness and safety of chondroitin for ophthalmologic uses.
  • Use cautiously if allergic or hypersensitive to chondroitin sulfate products. Use cautiously in patients with shellfish allergy, due to the possibility of allergic reaction. Hives, rash, sun skin sensitivity, and worsening of previously well-controlled asthma have been reported. Use cautiously with bleeding disorders and with blood-thinners like warfarin (like Coumadin®). Avoid with prostate cancer or increased risk of prostate cancer. Avoid if pregnant or breastfeeding.
  • Echinacea: Oral Echinacea purpurea may offer some benefits in people with low-grade uveitis. Further research is needed to confirm preliminary research findings.
  • Avoid if allergic to echinacea, its constituents, or any members of the Asteraceae/Compositae family (ragweed, chrysanthemums, marigolds, daisies). Use cautiously in patients prone to atopic reactions and in those with hemochromatosis and diabetes. Some natural medicine experts discourage the use of echinacea by people with conditions affecting the immune system, such as HIV/AIDS, some types of cancer, multiple sclerosis, tuberculosis, and rheumatologic diseases (such as rheumatoid arthritis or lupus). Use parenteral preparations of echinacea(no longer approved for use in Germany) cautiously. Use tinctures cautiously with alcoholic patients or in patients taking disulfiram or metronidazole. Avoid using echinacea in patients presenting for anesthesia. Use cautiously if pregnant or breastfeeding.
  • Eyebright: In Europe, the herb eyebright (Euphrasia officinalis) has been used for centuries as a rinse, compress, or bath against eye infections and other eye-related irritations (a use reflected in many of its vernacular names). When taken by mouth, eyebright has been used to treat inflammation of nasal mucous membranes and sinusitis. Eyebright has been used in ophthalmic (eye) solutions for centuries, in the management of multiple eye conditions. Currently, there is insufficient available scientific evidence for or against the use of eyebright in the treatment of conjunctivitis.
  • Avoid in individuals with a known allergy or hypersensitivity to eyebright. Hypersensitivity to members of the Scrophulariaceae family may lead to a cross-sensitivity reaction. Use cautiously as an eye treatment, particularly homemade preparations, due to the risk of infection if not sterile. Use cautiously with diabetes and drugs that are broken down by the liver. Avoid if pregnant or breastfeeding.
  • Flaxseed and flaxseed oil: Taking flaxseed oil capsules by mouth may reduce keratoconjunctivitis sicca (dry eye) associated with Sjogren’s syndrome patients.
  • Flaxseed has been well-tolerated in studies for up to four months. Avoid if allergic to flaxseed, flaxseed oil or other plants of the Linaceae family. Avoid large amounts of flaxseed by mouth and mix with plenty of water or liquid. Avoid flaxseed (not flaxseed oil) with a history of esophageal stricture, ileus, gastrointestinal stricture or bowel obstruction. Avoid with a history of acute or chronic diarrhea, irritable bowel syndrome, diverticulitis or inflammatory bowel disease. Avoid topical flaxseed in open wounds or abraded skin surfaces. Use cautiously with history of a bleeding disorder or with drugs that cause bleeding risk (like anticoagulants and non-steroidal anti-inflammatories (like aspirin, warfarin, Advil®)), high triglyceride levels, diabetes, mania, seizures or asthma. Avoid if pregnant or breastfeeding. Avoid with prostate cancer, breast cancer, uterine cancer, or endometriosis. Avoid ingestion of immature flaxseed pods.
  • Grape seed: Several small studies suggest that grape seed (Vitis vinifera) may slow the progression of retinopathy (damage to the retina caused by diabetes or high blood pressure). Visual performance may be improved in healthy patients as well. Further research is needed to better determine the effectiveness of grape seed for vision problems.
  • There are reports of people with allergy to grapes or other grape compounds, including anaphylaxis. Individuals allergic to grapes should not take grape seed and related products. Use cautiously if taking anticoagulants. Use cautiously with blood pressure disorders or if taking ACE inhibitors. Grape seed may interfere with the way the body processes certain drugs that use the liver’s cytochrome P450 enzyme system. Avoid if pregnant or breastfeeding.
  • Kinetin: Kinetin is a chemical analogue of cytokinins, a class of plant hormones that promotes cell division. Kinetin is found in both plants and animals. Kinetin may be effective for decreasing ocular blood pressure, although currently there is insufficient available evidence to make a strong conclusion. More research is needed in this area.
  • Avoid if allergic or hypersensitive to kinetin. Use cautiously with coagulation or hematologic (blood) disorders or if taking anticoagulants or antiplatelets (blood thinners). Avoid if pregnant or breastfeeding.
  • Lutein: Lutein and zeaxanthin are found in high levels in foods such as green vegetables, egg yolk, kiwi fruit, grapes, orange juice, zucchini, squash, and corn. For some commercially available supplements, lutein is extracted from marigold petals. Spinach and collard greens, both rich in lutein, are associated with a reduced risk for age-related macular degeneration. However, preliminary evidence does not support a link between levels of lutein in the body and reduced risk for lens opacities. More research is required.
  • Avoid in individuals with a known allergy or hypersensitivity to lutein or zeaxanthin. Use cautiously if at risk for cardiovascular disease or cancer. Avoid if pregnant or breastfeeding.
  • Propolis: Propolis is a natural resin created by bees, used in the construction of hives. Propolis is produced from the buds of conifer and poplar tress, in combination with beeswax and other bee secretions. Laboratory studies suggest anti-viral and anti-inflammatory activity of propolis. There is limited poor-quality study of propolis for the treatment of corneal complications of varicella zoster, reporting faster healing and improvement of sight. Better human research is needed.
  • Patients who have had an allergic/hypersensitivity reaction to propolis, Populus nigra L. (black poplar), poplar bud, bee stings/bee products (including honey), or Balsam of Peru should avoid propolis. There are multiple reports of swelling, fluid collection, redness, burning, eczema, swelling, fever, and other allergic reactions with the repeated use of propolis on the skin. Use cautiously with asthma or gastrointestinal disorders. Avoid if pregnant or breastfeeding because of the high alcohol content in some products.
  • Rose hips: Rose hips are the fruits that develop from the blossoms of the wild rose (Rosa spp.). They are typically orange to red in color, but some species may be purple or black. Preliminary evidence suggests that an herbal formula (Ophthcare®) containing rose hips may help treat a variety of ophthalmologic disorders. Additional study is needed to determine if rose hips are an effective treatment for these indications.
  • Avoid in individuals with a known allergy/hypersensitivity to Rosa spp., rose hip dust, its constituents, or members of the Rosaceae family.
  • Selenium: Although selenium appears to be involved in cataract development and uveitis (eye inflammation), it is not known whether selenium supplements may affect the risk of developing these eye disorders. Additional research in this area is warranted.
  • Avoid with history of nonmelanoma skin cancer. Selenium is generally regarded as safe for pregnant or breastfeeding women. However, animal research reports that large doses of selenium may lead to birth defects.
  • Spirulina: Blue-green algae may help treat blepharospasm (eyelid twitch or spasm) but additional high-quality research is necessary to make a recommendation.
  • Avoid if allergic or hypersensitive to spirulina or blue-green algae. Use cautiously with phenylketonuria (a genetic disorder of a liver enzyme that disrupts normal body functions), autoimmune diseases, bleeding disorders, diabetes, and osteoporosis. Use cautiously with products containing the blue-green algae species Anabaena spp., Aphanizomenon spp., and Microcystis spp.; in underweight patients or in those taking antiobesity agents or appetite suppressants; and if consuming a high-protein diet. Avoid in children and if pregnant or breastfeeding.
  • Taurine: Taurine, or 2-aminoethanesulfonic acid, was originally discovered in ox (Bos taurus) bile and was named after taurus or bull. A nonessential amino acid-like compound, taurine, is found in high abundance in the tissues of many animals, especially sea animals, and in much lower concentrations in plants, fungi, and some bacteria. Taurine supplementation may reduce visual fatigue due to visual display terminals. More search is needed to make a conclusion.
  • Taurine is an amino acid and it is unlikely that there are allergies related to this constituent. However, allergies may occur from multi-ingredient products that contain taurine. Use cautiously in patients with high cholesterol, low blood pressure, coagulation disorders, potential for mania, or epilepsy. Avoid exercise or alcohol after consumption of energy drinks containing taurine, caffeine, glucuronolactone, B vitamins, and other ingredients. Use cautiously if pregnant or breastfeeding because taurine is a natural component of breast milk.
  • Tea tree oil: Early studies found that tea tree oil may be an effective treatment for ocular demodex (parasitic mites). Large, well-designed clinical trials are needed before a strong recommendation can be made.
  • Avoid if allergic or hypersensitive to tea tree oil (Melaleuca alternifolia), any of its constituents, balsam of Peru, benzoin, colophony (rosin) tinctures, eucalyptol, or members of the Myrtle (Myrtaceae) family. Avoid taking tea tree oil by mouth. Avoid if taking antineoplastic agents. Use tea tree oil applied to the skin cautiously in patients with previous tea tree oil use. Avoid if pregnant or breastfeeding.
  • Thymus extract: Thymus extracts for nutritional supplements are usually derived from young calves (bovine). Bovine thymus extracts are found in capsules and tablets as a dietary supplement. Preliminary evidence suggests that thymus extract, in addition to local treatment, reduces the recurrence rate of keratitis. Further well-designed clinical trials are still required.
  • Avoid in individuals with a known allergy or hypersensitivity to thymus extracts. A severe anaphylactic reaction to injected thymostimulin has been documented in a case report. Allergy to thymic extracts has not been demonstrated in currently available clinical trials. Use bovine thymus extract supplements cautiously due to potential for exposure to the virus that causes “mad cow disease.” Avoid use with an organ transplant or other forms of allografts or xenografts. Avoid if receiving immunosuppressive therapy, with thymic tumors, myasthenia gravis (neuromuscular disorder), untreated hypothyroidism, or if taking hormonal therapy. Avoid if pregnant or breastfeeding; thymic extract increases human sperm motility and progression.
  • Turmeric: Poorly designed human study suggests a possible benefit of curcumin (from Curcuma longa) in the treatment of uveitis (eye inflammation). Reliable human research is necessary before a firm conclusion can be drawn.
  • Allergic reactions to turmeric may occur, including contact dermatitis (an itchy rash) after skin or scalp exposure. People with allergies to plants in the Curcuma genus are more likely to have an allergic reaction to turmeric. Use cautiously in patients allergic to turmeric or any of its constituents (including curcumin), to yellow food colorings, or to plants in the Zingiberaceae (ginger) family. Turmeric may also increase bleeding in sensitive individuals, including those taking blood thinning medications such as aspirin and warfarin (Coumadin®). Avoid in medicinal amounts if pregnant or breastfeeding. Turmeric should be stopped prior to scheduled surgery.
  • Vitamin A: High-dose vitamin A supplementation in addition to vitamin E has been suggested to help improve ocular healing after photoreactive keratectomy, a type of laser eye surgery used to correct nearsightedness, and to improve visual acuity. Additional evidence is necessary before a definitive conclusion can be reached.
  • Vitamin A toxicity, or hypervitaminosis A, is rare in the general population. Vitamin A toxicity can occur with excessive amounts of vitamin A taken over short or long periods of time. Consequently, toxicity can be acute or chronic. An infant with acute toxicity can develop a bulging fontalle (the soft spot on the head) and symptoms similar to a brain tumor. Adults experience less specific symptoms such as headache, dizziness, fatigue, malaise, blurry vision, bone pain and swelling, nausea, and/or vomiting. Severe toxicity can lead to eye damage, high levels of calcium, and liver damage. Persons with liver disease and high alcohol intake may be at risk for hepatotoxicity from vitamin A supplementation. Smokers who consume alcohol and beta-carotene may be at an increased risk for lung cancer or cardiovascular disease.
  • Vitamin E: Vitamin E is a fat-soluble vitamin with antioxidant properties. High-dose vitamin E plus vitamin A (taken by mouth) may improve healing after photorefractive keratectomy. Additional research is necessary before this use of vitamin E can be concluded as being safe or effective. Four-month oral supplementation with vitamin E had no apparent effect on uveitis-associated macular edema or visual acuity in limited available study. High quality clinical research is needed.
  • Vitamin E may increase bleeding in sensitive individuals, including those taking blood thinning medications, such as aspirin and warfarin (Coumadin®). Avoid if allergic or hypersensitive to vitamin E. Avoid with retinitis pigmentosa (loss of peripheral vision). Avoid above the recommended daily level in pregnant women and breastfeeding women.
  • Fair negative scientific evidence:
  • Vitamin E: Oral vitamin E does not appear to slow visual decline in people with retinitis pigmentosa and may be associated with more rapid loss of visual acuity, although the validity of this finding has been questioned. Until further evidence is available, vitamin E may not be advisable in this condition. Therapy decisions should be under medical supervision.
  • Strong negative scientific evidence:
  • Vitamin B12: Vitamin B12 is an essential water soluble vitamin that is commonly found in a variety of foods such as fish, shellfish, meats, and dairy products. Vitamin B12 is frequently used in combination with other B vitamins in a vitamin B complex formulation. Vitamin B12 can cause severe and swift optic atrophy and is contraindicated in early Leber’s disease (hereditary optic nerve atrophy).


  1. American Academy of Family Physicians. .
  2. American Academy of Ophthalmology. .
  3. Gutteridge IF, Hall AJ. Acute anterior uveitis in primary care. Clin Exp Optom. 2007;90(2):70-82.
  4. National Eye Institute. .
  5. Natural Standard: The Authority on Integrative Medicine. .
  6. Owsley C, McGwin G. Measuring the personal burden of eye disease and vision impairment. Ophthalmic Epidemiol. 2007;14(4):188-91.
  7. Patel PB, Diaz MC, Bennett JE, et al. Clinical features of bacterial conjunctivitis in children. Acad Emerg Med. 2007;14(1):1-5.
  8. Swamy BN, Chilov M, McClellan K, et al. Topical non-steroidal anti-inflammatory drugs in allergic conjunctivitis: meta-analysis of randomized trial data. Ophthalmic Epidemiol. 2007;14(5):311-9.
  9. University of Illinois Eye and Ear Infirmary. .

Prevention and self-management

  • Any changes in the appearance of the eyes or vision should be investigated further. Some examples include: unusual trouble adjusting to dark rooms; difficulty focusing on near or distant objects; squinting or blinking due to unusual sensitivity to light or glare; change in color of iris; red-rimmed, encrusted, or swollen lids; recurrent pain in or around eyes; double vision; dark spot at the center of viewing; lines and edges appear distorted or wavy; excess tearing or “watery eyes;” dry eyes with itching or burning; and seeing spots or ghost-like images.
  • Proper hygiene: Practicing good hygiene is the best way to control the spread of conjunctivitis. Once the infection has been diagnosed, follow these steps: do not touch the eyes with the hands; wash hands thoroughly and frequently; change towels and washcloths daily and do not share them with others; change the infected individual’s pillowcase often; discard eye cosmetics, particularly mascara; do not use anyone else’s eye cosmetics or personal eye-care items; follow an eye doctor’s instructions on proper contact lens care. If a child is infected, avoid close contact with other children. Many schools send children with conjunctivitis home.
  • Eye rinsing: In cases of minor irritation, such as irritation resulting from a piece of dust flying into the eye, the individual may be able to wash out the foreign object from the eye with clean tap water. Rinsing the eye is best done by tilting the head back and pouring water into the opened eye. The individual can also fill a clean sink with water and plunge the head into the water with the eyes open. Make sure no chemicals, such as bleach, are used to clean the sink before rinsing the eyes – only soap and water. Laboratories and industrial settings where chemical contaminations are possible have eye wash stations to rinse out the eyes if necessary.
  • Over-the-counter (OTC) medications: Over-the-counter (OTC) artificial tears or lubricants may improve the discomfort in the eye.
  • Over-the-counter pain (OTC) medicine, such as acetaminophen (Tylenol®) or ibuprofen (Advil®), may be helpful if pain and inflammation is present. If a few doses of the medication do not bring relief, consult an ophthalmologist.
  • Eye examination: Regular eye exams are imperative to detecting vision changes early enough for successful treatment. It is best to have routine eye checkups every two to four years after age 40 and every one to two years after age 65. Recommended scheduled eye examinations include: before age five, toddlers should be screened for common childhood problems such as crossed eye, lazy eye, nearsightedness, and farsightedness; puberty to age 39, individuals should be checked if they experience any eye problems or visual changes such as pain, floaters, flashes of light, blurry vision, or eye injury; ages 40-65, individuals should get an eye examination every two to four years; and over 65, individuals should get an eye examination every one to two years. Those at higher risk for eye diseases need to be examined more often. For example, adults with diabetes should have yearly eye exams. Other people at higher risk include blacks over age 40 (due to an increase incidence of high blood pressure and diabetes), people with a family history of eye disease, or those with a history of eye injury.
  • Diet: Eating a healthy diet full of fruits and vegetables helps to ensure that enough vitamins and minerals are consumed for use by the body and eyes. Some that are especially important to eye health include vitamin A, vitamin C, vitamin E, and zinc. Lutein is a naturally occurring carotenoids found in green leafy vegetables such as spinach and kale. Lutein is used as an antioxidant and has been reported especially important for eye health.
  • Drinking fluids in small amounts over the course of a day can help individuals with increased intraocular pressure (IOP). Drinking a quart or more of any liquid within a short time may increase eye pressure. Limiting caffeine to low or moderate levels may be helpful.
  • Smoking cessation: Smoking produces free radicals that cause oxidation to body tissues including the eyes. Smoking increases the risk of eye conditions such as cataracts and macular degeneration.
  • Sun protection: Ultraviolet light may contribute to the development of eye problems, including cataracts. Whenever possible, wear sunglasses and sunscreen when outdoors. Anti-glare sunglasses and those with ultraviolet (UV) protection are recommended by healthcare professionals.
  • If the individual is pregnant and suspects that they may have a sexually transmitted disease, it is essential to be checked and possibly treated for any infection prior to the birth of the baby.
  • Health conditions: Other health conditions, such as diabetes, may increase the risks for eye conditions such as cataracts and diabetic retinopathy. Making sure blood sugar levels are controlled is important for eye health.
  • Genetic and medical counseling: Genetic counseling may be recommended for people with family histories of genetic eye disorders. In addition, laboratory testing may determine if a person is a carrier for a particular genetic eye disorder.

Structure and function of the eye

  • The eye:
  • The eye is a hollow, fluid-filled, three-layered ball. The outer layer is the sclera, the innermost is the retina (the thin light-gathering layer), and the middle layer is the uvea. The uvea is made up of the iris, the ciliary body, and the choroid.
  • The eyeball is divided into two sections, each of which is filled with fluid. The front section (anterior segment) extends from the inside of the cornea to the front surface of the lens. It is filled with a fluid called the aqueous humor, which nourishes the internal structures. The back section (posterior segment) extends from the back surface of the lens to the retina. It contains a jellylike fluid called the vitreous humor. The pressure generated by these fluids fills out the eyeball and helps maintain its shape.
  • The anterior segment itself is divided into two chambers. The front (anterior) chamber extends from the cornea to the iris; the back (posterior) chamber extends from the iris to the lens. Normally, the aqueous humor is produced in the posterior chamber, flows slowly through the pupil into the anterior chamber, and then drains out of the eyeball through outflow channels located where the iris meets the cornea.
  • Light and image transmission:
  • Light enters the eye through the cornea, a transparent dome on the front surface of the eye. The cornea serves as a protective covering for the front of the eye and also helps focus light on the retina at the back of the eye. After passing through the cornea, light travels through the pupil (the black dot in the middle of the iris), which is actually a hole through the iris. The iris is the circular, colored area of the eye and controls the amount of light that enters the pupil. The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle. These muscles contract to either dilate (enlarge) or constrict (shrink) the size of the pupil. The iris allows more light into the eye when the environment is dark and allows less light into the eye when the environment is bright.
  • Behind the iris sits the lens. Through the action of small muscles (called the ciliary muscles), the lens becomes thicker to focus on nearby objects and thinner to focus on distant objects. By changing its shape, the lens focuses light onto the retina.
  • The retina contains the photoreceptors, which are nerve cells, and the blood vessels that nourish them. The most sensitive part of the retina is a small area called the macula, which has millions of tightly packed photoreceptors. The density of photoreceptors in the macula allows for highly detailed visual images. All photoreceptors are connected to individual nerves, which bundle together to form the optic nerve. The optic nerve begins at the optic disk, a small round structure at the back of the eye. The photoreceptors in the retina convert the image into electrical impulses, which are carried to the brain by the optic nerve.
  • There are two main types of photoreceptors, cones and rods. Cones are clustered mainly in the macula and are responsible for color vision as well as sharp, detailed central vision. The rods are responsible for night and peripheral (side) vision. Rods are more numerous than cones and much more sensitive to light, but they do not register color. Rods are grouped mainly in the peripheral areas of the retina and do not contribute to detailed central vision as do the cones.
  • Protective structures:
  • The bony structures of the orbit protrude beyond the surface of the eye. They protect the eye while allowing it to move freely in a wide arc.
  • The eye has a relatively tough white outer layer (sclera or white of the eye). Near the front of the eye, the sclera is covered by a thin mucous membrane (conjunctiva), which runs to the edge of the cornea and also covers the moist back surface of the eyelids.
  • The eyelashes are short, tough hairs that grow from the edge of the eyelid. The upper lashes are longer than the lower lashes and turn upward. The lower lashes turn downward. Eyelashes keep insects and foreign particles away from the eye by acting as a physical barrier and by causing the person to blink reflexively at the slightest disturbance.
  • The upper and lower eyelids are thin flaps of skin that can cover the eye. They reflexively close quickly (blink) to form a mechanical barrier that protects the eye from foreign objects, wind, dust, insects, and very bright light. The reflex is triggered by the sight of an approaching object, the touch of an object on the surface of the eye, or the eyelashes being exposed to wind or small particles such as dust or insects. On the moist back surface of the eyelid, the conjunctiva loops around to cover the front surface of the eyeball, right up to the edge of the cornea. The conjunctiva protects the sensitive tissues underneath it.
  • When an individual blinks, the eyelids help spread tears over the surface of the eye. Tears consist of a salty fluid that continuously bathes the surface of the eye to keep it moist and transfers oxygen and nutrients to the cornea, which lacks blood vessels that normally supply these substances to other tissues. When closed, the eyelids help trap the moisture against the surface of the eye. Small glands at the edge of the upper and lower eyelids secrete an oily substance that contributes to the tear film and keeps tears from evaporating. Tears also trap and sweep away small particles that enter the eye. Moreover, tears are rich in antibodies that help prevent infection. The eyelids and tears protect the eye while allowing clear access to light rays entering the eye. If allowed to dry, the transparent cornea may become injured, infected, or opaque.
  • The lacrimal glands, located at the top outer edge of each eye, produce the watery portion of tears. Mucous glands in the conjunctiva produce mucus, which mixes with the watery portion of the tears to create a more protective tear film. Tears drain from each eye into the nose through one of the two nasolacrimal ducts; each of these ducts has openings at the edge of the upper and lower eyelids near the nose, called the punctum.

Common eye disorders

  • Age-related eye disorders:
  • Scleral changes: Years of exposure to ultraviolet light, wind, and dust may cause changes to the sclera (the white of the eyes) late in life. These changes may include yellowing or browning, random splotches of pigment (more common in people with a dark complexion), or a bluish hue due to increased transparency of the sclera.
  • Dry eye: The number of mucous cells in the conjunctiva may decrease with age. Tear production may also decrease with age, so that fewer tears are available to keep the surface of the eye moist. Both of these changes explain why older people are more likely to have dry eyes.
  • Arcus senilis: Arcus senilis (a deposit of calcium and cholesterol salts) appears as a gray-white ring at the edge of the cornea. It is common in people older than 60. Arcus senilis does not affect vision.
  • Retinal disorders: Some diseases of the retina are more likely to occur in old age, including macular degeneration, diabetic retinopathy, and retinopathy. Other eye diseases, such as cataracts, also become common. Please see individual condition monographs for more information on these eye disorders.
  • Ectropion: The muscles that squeeze the eyelids shut decrease in strength with age; this, combined with gravity and age-related looseness of the eyelids, sometimes results in the lower eyelid falling away from the eyeball, a condition called ectropion. In rare cases, ectropion may be present at birth. In such instances, ectropion is usually associated with genetic disorders such as Down syndrome.
  • Puffy eyelids: In some older people, the fat around the orbit shrinks, causing the eyeball to sink into the orbit. Because of lax tissues in the eyelids, the orbital fat can also bulge forward into the eyelids making them appear constantly puffy.
  • The muscles that work to regulate the size of the pupils weaken with age. The pupils become smaller, react more sluggishly to light, and dilate more slowly in the dark. Therefore, people older than 60 may find that objects are not as bright, that they are dazzled initially when going outdoors (or when facing oncoming cars during night driving), and that they have difficulty going from a brightly lit environment to a darker one. These changes may be particularly bothersome when combined with the effects of a cataract.
  • Other changes in eye function also occur as people age. The sharpness of vision (acuity) is reduced despite use of the best glasses, especially in people who have a cataract, macular degeneration, or advanced glaucoma. The amount of light that reaches the back of the retina is reduced, increasing the need for brighter illumination and for greater contrast between objects and the background.
  • Vision problems:
  • 20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If an individual has 20/20 vision, they can see clearly at 20 feet what should normally be seen at that distance. If the individual has 20/100 vision, it means that they must be as close as 20 feet to see what a person with normal vision can see at 100 feet.
  • 20/20 does not necessarily mean perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. There are other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability, and color vision that contribute to the individual’s overall visual ability.
  • Some people can see well at a distance, but are unable to bring nearer objects into focus. This condition can be caused by hyperopia (farsightedness) or presbyopia (loss of focusing ability). Others can see items that are close, but cannot see those far away. This condition may be caused by myopia (nearsightedness).
  • There are many types of visual disturbances. These include blurred vision, halos, blind spots, floaters, and other symptoms. Blurred vision is the loss of sharpness of vision and the inability to see small details. Blind spots (scotomas) are dark “holes” in the visual field in which nothing can be seen.
  • Changes in vision, blurriness, blind spots, halos around lights, or dimness of vision should always be evaluated by a healthcare professional. Such changes may represent an eye disease, aging, eye or brain injury, or a condition like diabetes that affects many organs in the body. Whatever the cause, vision changes should never be ignored. Vision problems can get worse and significantly impact the quality of the individual’s life.
  • Astigmatism: Astigmatism simply refers to a very common eye condition in which the eye curves more steeply on one side than the other, so that the cornea is oval or “football” shaped. Astigmatism causes light rays to focus at two different points in the eye which causes distant and near images to be blurred. Most cases of astigmatism are inherited and present at birth or early childhood. Other cases may develop secondary to other eye conditions or as a result of a traumatic injury to the cornea.
  • Myopia: Myopia, or nearsightedness, is probably the most common type of vision disturbance, affecting about one in four people in the United States. Individuals with myopia can see things up close (this may be as little as a few inches), but anything further away appears blurry or even indistinguishable. With myopia, the eyeball is too long, or the cornea is too steep, so images are focused in the vitreous inside the eye rather than on the retina at the back of the eye. This causes blurred vision. Having a family history of myopia is one of the most well-known risk factors for myopia. It has been estimated that as few as 6-15% of people with myopia have no family history of the disorder. Some experts suspect that people may inherit a tendency to develop myopia, but a combination of genetic and environmental factors determine whether or not a person actually develops the condition. Genetic markers on chromosomes 1, 2, 12, and 18 have been linked to myopia, although specific genes have not been identified.
  • Hyperopia: Hyperopia, or farsightedness, results from an eye that is too short, meaning that light rays reach the retina before they have the opportunity to converge into a focused image. Individuals with this condition are able to see, with varying degrees of success, objects further away, but close-up items are blurry.
  • Presbyopia: Presbyopia, or double vision, is difficulty focusing on objects that are close. In middle age (usually starting in the middle 40s), the lens of the eye becomes less flexible and less able to thicken. The eyes become less able to focus on nearby objects, a condition called presbyopia. Reading glasses, or bifocal lenses, can help compensate for this problem.
  • Currently, an estimated 90 million people in the United States either have presbyopia or will develop it by 2014.
  • Floaters: Floaters are tiny particles drifting across the eye. Eye floaters look like black or gray specks, strings, or cobwebs that drift about when the individual moves their eyes. Most eye floaters are caused by age-related changes that occur as the jelly-like substance (vitreous) inside the eyes becomes more liquid. When this happens, microscopic fibers within the vitreous tend to clump together. These clumps of debris float around within the vitreous cavity, and they can cast tiny shadows on the retina, which the individual may see as floaters. Eye floaters are most noticeable when the individual looks at a plain bright background such as a blue sky or a plain white wall. Although often brief and harmless, they may be a sign of retinal detachment. Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Eye floaters tend to affect those over age 40. Other risk factors for eye floaters include nearsightedness, eye trauma, complications from cataract surgery, diabetic retinopathy, and eye inflammation.
  • Other vision problems: Other potential causes of vision problems include fatigue, overexposure to the outdoors (temporary and reversible blurring of vision), and many medications. Medications that can affect vision, including causing blurry vision and dry, irritated eyes, include: antihistamines (such as diphenhydramine or Benadryl®), anticholinergics (such as dicyclomine or Bentyl®), digitalis derivatives (such as digoxin or Lanoxin®), some high blood pressure pills (guanethidine, reserpine, and thiazide diuretics), indomethacin (Indocin®), phenothiazines (such as prochlorperazine or Compazine®), and medications for malaria (such as chloroquine or Aralen®) and tuberculosis (including ethambutol or Myambutol®).
  • Conjunctivitis:
  • Conjunctivitis, or pink eye, is an inflammation or infection of the transparent membrane (conjunctiva) that lines the eyelid and part of the eyeball. The cause of pink eye is usually a bacterial or viral infection, and it is often associated with colds. Both viral and bacterial types are very contagious. Conjunctivitis can also be caused by an allergic reaction. In newborns, an incompletely opened tear duct may lead to conjunctivitis. Blocked tear ducts may also lead to conjunctivitis.
  • Bacterial conjunctivitis: The most common types of bacteria that cause bacterial conjunctivitis include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, and Pseudomonas aeruginosa. Bacterial conjunctivitis is usually associated with a thick discharge or pus and can affect one or both eyes. Bacterial conjunctivitis often produces a thick, yellow-green discharge and may be associated with a respiratory infection or with a sore throat. Adults and children alike can develop both of these types of pink eye. However, bacterial conjunctivitis is more common in children than it is in adults.
  • Viral conjunctivitis: Viral conjunctivitis is a common type of conjunctivitis caused by a viral infection, such as the common cold or influenza viruses. Viral conjunctivitis is highly contagious, because airborne viruses can be spread through sneezing and coughing. Viral conjunctivitis also can accompany common viral upper respiratory infections such as measles, the flu, or the common cold. Viral conjunctivitis is usually associated with a watery discharge, and may affect both eyes. However, the infection typically starts in one eye and quickly spreads to the other eye.
  • Gonococcal and chlamydial conjunctivitis: Gonococcal or chlamydial conjunctivitis are caused by bacteria commonly associated with sexually transmitted diseases, including gonorrhea and chlamydia. Newborn babies may be exposed when they pass through the birth canal of an infected mother. Chlamydial conjunctivitis typically affects sexually active teens and young adults and is the most frequent infectious cause of neonatal conjunctivitis in the United States. The Centers for Disease Control (CDC) recognizes chlamydia as one of the major sexually transmitted pathogens, estimating approximately three million new cases per year. Women seem to be more susceptible than men, possibly due to differences in reproductive anatomy. The incidence of infection seems to be directly related to sexual activity and geography, with urban populations having higher incidences. The incidence in pregnant women overall is 4-10%. Trachoma is a form of chlamydial infection that causes the eye’s surface to become scarred. Trachoma is the world’s leading cause of preventable blindness.
  • Neonatal conjunctivitis: Most cases of neonatal conjunctivitis are caused by viruses. In newborns, conjunctivitis may also result from an incompletely opened tear duct. Neonatal conjunctivitis in newborn babies can cause blindness when left untreated.
  • Neonatal conjunctivitis can also be caused by herpes viruses, which are also associated with sexually transmitted diseases. Herpes simplex virus type 2 is most often found in the genital area and can infect the eyes of infants during birth. Herpes simplex virus type 1, more commonly associated with cold sores on the mouth, also can cause genital herpes and may thus also result in neonatal conjunctivitis.
  • Allergic conjunctivitis: Allergies can cause lead to a very common form of conjunctivitis, called allergic conjunctivitis. Allergens that can trigger allergic conjunctivitis (as well as other types of allergies) include pollen, animal dander, and dust mites. The most common symptom of allergic conjunctivitis is itching of the eyes. Itchy eyes may be relieved with special eye drops containing antihistamines, which block the histamines that cause allergic reactions. These eye drops are available by prescription or over-the-counter.
  • Non-infectious conjunctivitis: Conjunctivitis may be caused by non-infectious sources, smoke, diesel exhaust, perfumes, and chemical splashes. Discharge tends to be mucus rather than pus. Sometimes, flushing and cleaning the eye to rid it of the chemical or object causes redness and irritation. Signs and symptoms usually clear up on their own within about a day.
  • Certain forms of non-infectious conjunctivitis, including giant papillary conjunctivitis (GPC), can be caused by the eye’s immune responses to foreign objects such as contact lenses or ocular prosthetics (artificial eyes). Toxic conjunctivitis can be caused by allergic reactions to certain ingredients in eye drops or ointments, such as preservatives or other chemicals.
  • The eyes of newborns are susceptible to bacteria normally present in the mother’s birth canal. These bacteria cause no symptoms in the mother, but in rare cases, these bacteria can cause infants to develop a serious form of conjunctivitis known as ophthalmia neonatorum. This condition requires immediate treatment in order to preserve sight. For this reason, doctors or healthcare workers apply antibiotics to every newborn’s eyes as a preventative measure.
  • Uveitis:
  • When any part of the uvea becomes inflamed, then it is called uveitis. The most common type of uveitis is an iritis (anterior uveitis, or inflammation of the iris). Uveitis can be quite serious and may lead to permanent vision loss. Early diagnosis and treatment are important. Uveitis is most common in people ages 20-50. However, in some people, uveitis is associated with autoimmune disorders, such as rheumatoid arthritis or ankylosing spondylitis; inflammatory disorders, such as Crohn’s disease or ulcerative colitis; infections, such as syphilis, toxoplasmosis, or tuberculosis; eye injury, and certain cancers, such as lymphoma.
  • Xerophthalmia (dry eye):
  • Xerophthalmia,also known as keratoconjunctivitis sicca or commonly as dry eye, is a medical condition in which the eye fails to produce a sufficient amount of tears for lubrication. The more modern term is dysfunctional tear syndrome, as that covers the many causes of this very complex problem. Anything that disturbs either the production of tears and/or the quality of the tears leads to dry eye syndrome or dysfunctional tear syndrome.
  • Dry eye problems are extremely common with increasing age, although they are more common in women than men. About 10-14 million Americans have some form of this problem. With age, tear production and quality may decrease. There are several conditions and medications that can lead to dry eye syndrome or make it worse. These include autoimmune conditions such as rheumatoid arthritis; diabetes; thyroid disease; some genetic conditions such as Sjögren syndrome and Bell’s palsy; some ocular surgical procedures including cataract surgery, refractive surgery for vision correction, and glaucoma surgery; ocular allergies and allergies in general; certain oral medications such as diuretics, anti-allergy medications, beta blockers, sleeping pills, pain relievers, and anti-anxiety medications; wearing contact lenses, especially excessive wear, low-water contact lenses, and ill-fitting contact lenses; preservatives in many eye drops, such as thimerosal (mercury); high-wind and low-humidity conditions, not only outside but wind drafts from heaters, fans, or air conditioners aimed toward the eyes; prolonged reading, computer use, or viewing of television or movies; use of a CPAP (Continuous Positive Airway Pressure) device for treatment of sleep apnea; diseases that affect the ability of the eyelids to close fully such as Bell palsy or facial paralysis; a deficiency in vitamin A; surgery of the eyelids that causes greater exposure of the eye; bone marrow transplant; inflammatory diseases; and degenerations of the cornea (outer covering of the eye).
  • Keratitis:
  • Keratitis is an inflammation of the cornea, the transparent membrane that covers the colored part of the eye (iris) and pupil of the eye. Keratitis is generally the result of a corneal infection injury or severe dryness. Risk factors that increase the likelihood of developing this condition include: poor contact lens care; overuse of contact lenses; illnesses or other factors that reduce the body’s ability to overcome infection; cold sores, genital herpes, and other viral infections; crowded, dirty living conditions; poor hygiene; and poor nutrition (especially a deficiency of vitamin A, which is essential for normal vision).
  • Herpes simplex keratitis: Herpes simplex keratitis is caused by an infection by the herpes simplex virus types 1 and 2 and is a major cause of adult eye disease. Herpes simplex keratitis may lead to chronic inflammation of the cornea; development of tiny blood vessels in the eye; scarring; loss of vision; and glaucoma. Herpes simplex keratitis generally begins with infection and inflammation of the membrane lining the eyelid (conjunctiva) and the portion of the eyeball that comes into contact with it. It usually occurs in one eye. Subsequent infections are characterized by a pattern of lesions that resemble the veins of a leaf. These infections are called dendritic keratitis and aid in the diagnosis.
  • Recurrences may be brought on by stress, fatigue, or ultraviolet light (UV) exposure (such as outdoor activities especially on water, which reflects UV rays off of the surface). Repeated episodes of dendritic keratitis can cause sores, permanent scarring, and numbness of the cornea. Recurrent dendritic keratitis is often followed by disciform keratitis. This condition is characterized by clouding and deep, disc-shaped swelling of the cornea and by inflammation of the iris. It is very important not to use topical corticosteroids with herpes simplex keratitis as it can make it much worse, possibly leading to blindness.
  • Bacterial keratitis: Bacterial keratitis is keratitis caused by bacteria including Streptococcus, Pseudomonas, Enterobacteriaceae (including Klebsiella, Enterobacter, Serratia, and Proteus), and Staphylococcus species. In bacterial keratitis, individuals wake up with their eyelids stuck together. There may be pain, sensitivity to light, redness, tearing, and a decrease in vision. This condition, which is usually aggressive, can result from improper use of contact lenses. Overnight wear of contact lenses can increase the risk of bacterial keratitis by 10-15 times more than if wearing daily wear contact lenses. Improper lens care, such as not cleaning and storing properly, is also a factor. Contaminated makeup can also contain bacteria. Bacterial keratitis makes the cornea cloudy due to infection and inflammation. It may also cause abscesses to develop in the stroma, which is located beneath the outer layer of the cornea.
  • Fungal keratitis: Fungal keratitis is a serious and painful corneal disease that is caused by fungal infection. Fungal keratitis is usually a consequence of injuring the cornea in a farm-like setting or in a place where plant material contaminated with fungi is present. Fungal keratitis often develops slowly. This condition usually affects people with weakened immune systems and often results in infection within the eyeball.
  • Peripheral ulcerative keratitis: Peripheral ulcerative keratitis is also called marginal keratolysis or peripheral rheumatoid ulceration. This condition is often associated with active or chronic rheumatoid arthritis, relapsing polychondritis (connective-tissue inflammation), and Wegener’s granulomatosis (a rare condition characterized by kidney disease and development of nodules in the respiratory tract).
  • Superficial punctate keratitis: Superficial punctuate keratitis is often associated with the type of viruses that cause upper respiratory infection (adenoviruses). It is characterized by destruction of pinpoint areas in the outer layer of the cornea (epithelium). One or both eyes may be affected.
  • Acanthamoeba keratitis: Acanthamoeba keratitis is an eye infection caused by Acanthamoeba. Acanthamoeba keratitis is a pus-producing condition that is very painful. It is a common source of infection in people who wear soft or rigid contact lenses. It can be found in tap water, soil, and swimming pools.
  • Photokeratitis: Photokeratitis or snowblindness is caused by excess exposure to UV light and a resulting burn of the cornea. This can occur with sunlight, sun tanning lamps, or a welding arc. It is called snow blindness because the sunlight is reflected off of the snow. It therefore can occur in water sports as well, because of the reflection of light off of the water. It is very painful and may occur several hours after exposure. It may last one to two days.
  • Interstitial keratitis: Also called parenchymatous keratitis, interstitial keratitis is a chronic inflammation of tissue deep within the cornea. Interstitial keratitis is rare in the United States. Interstitial keratitis affects both eyes and usually occurs as a complication of congenital or acquired syphilis. In congenital syphilis, it can occur between age two and puberty. It may also occur in people with tuberculosis, leprosy, or other diseases.
  • Other eye disorders:
  • Corneal abrasion: A corneal abrasion is a painful scrape or scratch of the surface of the clear part of the eye known as the cornea. This transparent window covers the iris, the circular colored portion of the eye. The cornea has many nerve endings just under the surface, so that any disruption of the surface may be painful. A corneal abrasion may occur when an object, such as a piece of dirt, hits the eye. In addition to causing corneal injury, high-speed particles may penetrate the eye and injure deeper structures. Examples include pieces of metal fragments thrown by a grinding wheel or ashes from a hot cigarette. Corneal abrasions may also occur when the eyes are irritated or rubbed excessively. Wearing contact lenses longer than recommended may injure the corneal surface and cause a corneal abrasion.
  • Retinitis pigmentosa: Retinitis pigmentosa is actually the name given to a group of hereditary eye disorders, all of which involve the retina, the light-sensitive nerve layer that lines the back of the eye. All diseases classified as retinitis pigmentosa cause a progressive vision loss. The retinal defect may be found in the rod cells, which are found outside of the central retina. Rods help to transmit dim light and allow for peripheral vision. The retina’s cone cells may also be affected and/or the connection between the cells that compose the retina. Cone cells are a type of retinal cell found inside the center of the retina that help to transmit the color and detail of images.
  • Several different inherited retinal problems can cause retinitis pigmentosa. In most cases, the disorder is caused by a recessive gene. This means that one abnormal gene must be inherited from both parents. Some cases have also been linked to genetic mutations on the X chromosome. Other cases are caused by a dominant gene, which means that people develop the disorder if they inherit the mutated gene from just one parent. For example, an estimated 30% of autosomal dominant cases occur when there is a mutation in the gene that codes for rhodopsin, a pigment in the retina that is needed for vision. When the gene is mutated, rhodopsin does not form properly and photoreceptor cells die in the eyes.
  • Some patients have no family history of the disease. In such cases, the genetic mutation may occur randomly during the development of the egg, sperm, or embryo.
  • Other cases may occur as part of other genetic disorders, such as Bassen-Kornzweig disease, or Kearns-Sayre syndrome, Waardenburg syndrome, Alport syndrome, or Refsum disease.
  • Blepharitis: Blepharitis is an eye disorder whereby the margins of the eyelid, the parts of the eye where the eyelashes grow, are inflamed, causing itching, redness, swelling, and irritation. This disorder may be caused by oil gland malfunctioning (posterior blepharitis), seborrheic dermatitis or excess growth of bacteria such as Staphylococcus bacteria (anterior blepharitis, staphlycoccal blepharitis), or allergies. Blepharitis may result in flaking of the skin around the eyes, crusted eyelashes, closed eyelids during sleep or upon wakening, sensitivity to light, or abnormal growth or loss of eyelashes. Blepharitis is usually treated, controlled, and prevented through proper ocular hygiene.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.
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